If had two batches of wort both with a OG of 1.050. The differrences being one has a 76% fermable sugars and the other has 65% fermable sugars. If I use an yeast with a 70% attenuation, what would the outcome be and what is the formula I would use. I already know the general answer that the 76% will ferment out to a lower FG, but trying to show in formula why.

To get you in the ballpark for your particular question, OG=1.050 w/ 76% attentuation, you would have 24% of the gravity remaining (100%-76%=24%). So then FG=1.050 * 0.24 = 1.012

It's very difficult to predict final gravity this way because there are so many variables that go into--amount of yeast pitched, health of the yeast, mashing program used, etc. So the above gives you an idea of where it might end up--it could be more, it could be less. The only way that I know for sure is to brew the recipe repeatedly so you know what to expect.

Deleted this message, have recieved email from White labs and confirmed there formula is same as Wyeast just done in another fashion, the -1 was meant as -1.0 and not as subtracting 1 point. My mistake. Here is the reply from White labs.
That is just the formula simplified, your probably doing it automatically by not using the 1 in your formula, for example instead of 1.060-1.010, your doing 60-10/60. But you can see how 1.060-1.010/1.060 won't work.

Last edited by brewmaster808 on Wed Jul 06, 2005 6:25 pm, edited 1 time in total.

Would this formula work, is it correct? Just pretend that there are no varibles. If I had two batches of wort both with a OG of 1.050. The differrences being one has a 76% fermable sugars and the other has 65% fermable sugars. If I use an yeast with a 70% attenuation